﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace PrintThePerInCircleOfGivenRadius
{
    class PrintThePerInCircleOfGivenRadius
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Insert a radius of Circle");
            string rad = Console.ReadLine();
            int a;
            double pi = Math.PI;
            if (int.TryParse(rad, out a))
            {
                Console.WriteLine("The perimeter is {0}",pi*2*a);
            }
            else 
            {
                Console.WriteLine("Invalid input");
            }
        }
    }
}
